The present invention relates generally to a boring tool or other device including thermal protection for an electronic component assembly and more particularly to an arrangement for thermally protecting the electronic component assembly by sensing temperature at a predetermined position relative to the assembly and disconnecting operational power therefrom when the sensed temperature reaches a maximum operating temperature such that the assembly may then survive in an unpowered state up to a higher maximum non-operating or storage temperature.
The use of horizontal boring tools has become increasingly popular. One contributing factor is the ever increasing underground installation of utility lines for reasons of aesthetics and for practical reasons such as, for example, protecting these lines from the effects of severe above ground weather conditions. In many cases it is undesirable to excavate an entire pathway for the purpose of installing such underground lines. For example, in areas where buried lines have previously been installed, such excavation many times results in the unintentional damage of an existing utility line. Therefore, boring tools may be utilized to avoid extensive excavation whereby to avoid unintentional damage to existing lines. Moreover, as guidance systems for horizontal boring tools become more and more sophisticated, the operator of a boring tool may avoid contact with such existing utility lines during a drilling operation by steering the tool around the line as it is approached.
It should be appreciated, however, that the increased sophistication of state of the art boring tools is attributable at least in part to the use of increasingly sophisticated electronic components which are positioned in the drill head of the boring tool. Typically, an electronic package in the drill head senses positional/orientation information relating to the underground guidance of the boring tool and transmits locating information to the surface using a telemetry transmitter. The package, like most other electronic assemblies, is sensitive to various environmental conditions including heat. Such heat may be produced by components which form part of the assembly and/or, as a result of the underground operation of the boring tool, as will be described immediately hereinafter.
During a particular boring operation, various underground soil conditions may be encountered by the boring tool including, for example, highly compacted soils or rock. When such a condition is encountered, significant frictional heat may rapidly be produced by interaction of the boring tool with the ground. This heat may cause the temperature of the boring tool to rise by hundreds of degrees in a time period less than one minute depending, of course, on how problematic the soil is. The electronic package housed in the drill head is then subjected to this heat in conjunction with its internally generated heat. In the past, there have been temperature sensing arrangements which, upon sensing a predetermined temperature, attempted to cope with this heat by shutting down only power to the output stage of the transmitter which drives the antenna housed in the drill head. However, protection offered to the electronic package by this arrangement was limited in that the rest of the system remained operational. Thus, there continues to be a need for improved thermal protection for electronic packages in boring tools and other devices.
As will be seen hereinafter, the present invention provides a highly advantageous arrangement and associated method for effectively providing an added margin of thermal protection for an electronic package within a boring tool or other devices including electronic packages which are subjected to similar thermal concerns.